INTRODUCTION. XXXl 
larval stage. In the younger form (Fig. 7) it is rudi- 
mentary, but scarcely more so than in Mera (Fig. 8). 


Fic. 6, 
Immediately posterior to the point of attachment of this 
organ with the alimentary canal are a series of muscular 
bands lying transversely across the latter, which probably 
fulfil the office of sphincter muscles by compressing the 
passage just posteriorly to the efferent orifice of this sup- 
posed urinary organ. Muscles very similar in appearance 
are situated near the terminal exit of the alimentary tube, 
and probably fulfil the office of sphincter muscles to the 
anal outlet. 
The contents of the appendage that we call the urinary 
organ are, under an object-glass of one-fifth focus, 
resolved into small round cells, containing a granular 
nucleus (Fig. 9). These cells are closely packed together, 

Fig. 7. Fia. 8. 
but not so as to lose their rounded character, and the 
whole are confined within stout walls. 
